This invention relates to rotary electrical machines and more particularly to an improved winding method and apparatus for the armature coils for such machines.
Rotating electrical machines have been proposed for many applications. For example they may be used as a starter motor for an internal combustion engine. In such an application, a DC electric motor is powered from a battery for starting the engine. The starter motor generally comprises a stator comprising a cylindrical yoke with a plurality of magnets circumferentially bonded to an inner surface of the yoke. An armature (rotor) having coils arranged opposite the magnets and supplied with electrical current for driving a rotating shaft of the armature forming a output shaft of the starter motor. The motor output shaft drives a crankshaft of the engine via a reduction gear, an overrunning clutch for starting the engine in a well known manner.
The magnets may be ordinary magnets obtained by magnetizing a ferrite type magnetic material. The coils are formed by winding a wire (in general, a thin wire having a diameter of 0.9 mm or less) on each of a plurality of radially arrayed magnetic pole teeth of the armature. These pole teeth have a general T-shape. At this time, the core pole teeth are covered with insulators around which the wire is wound.
However, if this thick wire is used in a conventional winding device, tension in winding becomes larger because of the wire thickness. As a result the wound wire does not slide smoothly along the guide plate and fails to enter the slots easily. Also the curvature of the wire during winding becomes larger to prevent smooth winding.
However, if the nozzle is simply moved on the outside of the slots along rectangular magnetic teeth in a looping fashion, the thick wire with a large curvature interferes with edges of the magnetic pole teeth. This prevents smooth winding because the wire is stretched around the coil end portions with a large pressing force and reaction from the curvature of the thick wire results in a high tension. Thus, the wound wire is not allowed to freely move into the entrances from the coil end portions, preventing formation of stable and uniform coils.
A first feature of this invention is adapted to be embodied in a winding method for an armature for rotary electric machines having a core with a plurality of radially extending magnetic pole teeth and wherein the pole teeth are circumferentially spaced to form with slots between adjacent magnetic pole teeth. The method comprising the steps of introducing a wire into a slot moving a strand of wire in a looping fashion around at least one magnetic pole teeth to form a coil continuously along the magnetic pole tooth nozzle on the outside circumferential side of the core. The looping comprising in succession an axial forward motion from one side face of the armature to the other side face of the armature when in registry with a first slot at one circumferential side of the pole tooth, a circumferential forward motion on the other side face of the of the armature to registry with a second slot, an axial return motion from the other side face of the armature to the one side face of the armature and a circumferential return motion to the first slot. In accordance with the invention, at least one of the circumferential motions extends past the registry with the respective slot and then back to registry therewith for introducing slack in the wire being wound.
Another feature of the invention is adapted to be embodied in a winding device for simultaneously winding a plurality of coils on the radially extending poles of an armature. The winding device comprises an annular needle ring having a shape complimentary to the armature. A plurality of needle openings pass radially through the needle ring for delivering a plurality of wires for winding around the pole teeth. A drive effects relative rotation and axial movement between the needle ring and an armature for looping the plurality of wires around the pole teeth.